1. Field of the Invention
The present invention relates to a differential case, and more particularly to a differential case for a differential equipped with a limited-slip mechanism
2. Description of the Relevant Art
Japanese Patent Publication No. 49(1974)-9848, for example, discloses a limited-slip differential in which differential pinions and side gears are housed in a differential case, and a multiple-disc clutch is interposed between each side gear and the differential case. The differential case has grooves defined axially in an inner peripheral surface thereof for preventing the rotation of and allowing the axial sliding movement of friction discs of the multiple-disc clutch.
The differential case comprises a bottomed cylindrical case body and a cover coupled to the open end of the case body. With the differential case thus assembled of two members, however, one end of each of the grooves that extend the full axial length of the differential case is positioned at the bottom of the differential case. Therefore, it is difficult to form these grooves by broaching, and the grooves must be formed by a more complex machining process. According to one disclosed design, friction discs are disposed only in the vicinity of the open end of the case body while no friction discs are positioned at the bottom thereof.
Another problem associated with the disclosed differential case is that it is subject to a higher surface pressure at the groove sections than at bearing sections by which drive shafts are rotatably supported on the differential case. Consequently, the material of the bottomed cylindrical case body must be selected to meet the mechanical strength which is required by the groove sections.
The present invention has been made in an effort to solve the aforesaid problems of the conventional differential case.